Adhesive composition for adhesion between fabric material and rubber and a process for preparation thereof

ABSTRACT

An adhesive composition for adhesion between fabric material and rubber is produced by a process in which a monohydric phenol is reacted with an aldehyde in the presence of an alkali metal hydroxide as a catalyst and neutralized with an acid; the resulting resinous material is dissolved in dilute ammonium hydroxide in the absence of free aldehyde and then mixed with a rubber latex.

United States Patent Honda et al. 1 May 20, 191

[ 1 ADHESIVE COMPOSITION FOR ADHESION I11 BETWEEN FAliRlC MATERIAL AND 0913) 5/1963 RUBBER AND A PROCESS FOR 3 338 769 M967 PREPARATION THEREOF 3.437.122 4/1969 Van Giles 260/2. 75 inventors: d Takehim Ueki; 3.480.066 11/1969 Meredith 156/3 Yuliio Fukuura, all of Tokyo. Japan [73] Assignee: Bridgestone Tire Co., Ltd., Tokyo, Primary Examiner-Lorenzo B. Hayes p n Attorney, Agent, or Firm--Fitzpatrick. Celia, Harpei 221 Filed: on. 1a, 1972 [21] Appl. No.: 298,584

[301 Foreign Appllcation Priority Data [57] ABSTRACT P 46'34373 An adhesive composition for adhesion between fab: material and rubber is produced by a process in whi US. Cl. ssssss es a monohydric is reacted an aldehyde 260/57 R3 260/845; 260/846 the presence of an alkali metal hydroxide as a cataly Ill. u and neutralized an the resulting re ino [58] Field of Search 260/293, 845, 846. 57 C, material is dissolved in dilute ammonium hydroxide 260/573; 156/335; H7/l38-8 N the absence of free aldehyde and then mixed with rubber latex. [56] References Cited UNITED STATES PATENTS 3 Claims No Drawings 2.609.352 9/1952 Kvalnes 260/57 R 1 ADHESIVE COMPOSITION FOR ADHESION BETWEEN FABRIC MATERIAL AND RUBBER AND A PROCESS FOR PREPARATION THEREOF BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to a novel adhesive composition used for adhering rubber to fabric material and a process for preparing said composition.

2. Description of the Prior Art When fabric materials such as nylon, vinylon, rayon, or polyester synthetic fibers are used as a reinforcing member for rubber articles such as pneumatic tires, belts, air cushions. hoses, or rubber vibration insulators, it is necessary to firmly adhere rubber compounds to these synthetic fabric materials. The adhesive composition used for treating a large quantity of fabric materials is preferably non-inflammable and nonpoisonous. From the above point of view, it is convenient and economical to use water as the medium for an adhesive composition. It is also desirable that the adhesive composition be durable and have a long shelf life.

As the conventional adhesive composition for this purpose, there may be mentioned a mixture ofa rubber latex and a condensed product obtained by the reaction of resorcinol with an aldehyde, particularly formaldehyde, in the presence of a catalyst such as an alkaline material or acid material (generally called RFI..").

' This RFL has been and is now widely used as an adhesive liquid suitable for mass production.

The amount of consumption of synthetic rubbers, particularly styrene-butadiene copolymer (SBR) has increased year by year. SBR is generally mixed with natural rubber (NR), but the compounding rate ofSBR tends to increase with the progress of rubber processing techniques and, furthermore, compositionsconsisting of SBR alone are now increasing.

When a blended composition of SBR and NR or a composition of NR alone is reinforced by a synthetic fabric material, a synthetic fabric material treated with RFL, which is believed to be ideal, is very effective for reinforcing a composition of NR alone and a blended composition of SBR and NR containing a high ratio of NR. When said synthetic fabric material is treated by RFL, however, it is not so effective for reinforcing a blended composition of SBR and NR containing a high ratio of SBR because the adhesive strength between the synthetic fabric material and the blended composition of SBR and NR containing a high ratio of SBR is low. Since such a low adhesive strength results in the shortening of the life of a rubber product subjected to a large, periodic deformation, it is desirable to prepare an adhesive composition having improved adhesive strength between SBR and a synthetic fabric material.

In a conventional process for producing RFL, resorcinol and formaldehyde are reacted in a solvent such as water in the presence of an alkaline catalyst and then latex is added after the reaction product reaches a certain degree of condensation. In general, excess, preferably l.25-2.5 moles, of formaldehyde is added to l mole of resorcinol. As the alkaline catalyst, there are used alkali metal hydroxides such as sodium hydroxide and potassium hydroxide or weak bases such as amines and, particularly, ammonium hydroxide; the resulting condensation product of resorcinol with formaldehyde belongs to the resol type.

1 sulfonic acid and'the like to produce a novolac tyr resin. The solution contairiing'the resin is made alkalir by adding an alkaline material such ascaustic soda ju before usei-formaldeh'yde is added until the quantii (mole) of formaldehyde becomes equal to, or great: than, that of resorcinol, andthen rubber latex is adde SUMMARY OF THE INVENTION According to the present invention, there is provide a process for the production of an adhesive compos tion for adhesion between fabric material and rubbe characterized in that a monohydric phenol is reacte with an aldehyde in the presence of an alkali metal h droxide as a catalyst, the mixture is dissolved in dilut ammonium hydroxide in the absence of free aldehyd and then mixed with a rubber latex.

According to another aspect of the present inventior there is provided an adhesive composition for adhesio between fabric material and rubber prepared by th process as described above. An object of this inventio is to provide a process for producing an adhesive con position giving good adhesion between fabric materi: and a blended composition of synthetic rubber and na ural rubber containing a high percentage of syntheti rubber or a composition of synthetic rubber alone. Ar other object of this invention is to provide an adhesiv composition capable of being used just after produc tion without storing or aging.

A further object is to provide a durable adhesiv composition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of this invention is as follows.

A monohydric phenol and aldehyde are reacted in solvent such as water and organic solvent, for exampl alcohols, ketones, esters, and aromatic hydrocarbon in the presence of an alkali metal hydroxide such as s dium hydroxide, potassium hydroxide, and the like, an then an acidic material such as an organic acid, for e: ample, acetic acid, formic acid, propionic acid, chlor acetic acid, glyoxylic acid, benzene sulfonic acid, 1 toluene sulfonic acid, and an inorganic acid, for exan pie, hydrochloric acid, carbonic acid, sulfuric acii boric acid, nitric acid, and phosphonic acid, is added 1 separate the resulting resin. The thus separated resin dissolvedin an aqueous solution of ammonium hydro: ide, or an amine compound having low boiling poin for example, methyl amine, dimethyl amine, trimeth amine, ethyl amine, diethyl amine, triethyl amine, l propyl amine, n-butyl amine, n-amyl amine and ti like, in the absence of free aldehyde, and thereafte rubber latex is added to prepare a liquid adhesive.

It has been new found that the adhesive compositic produced by the above described process has excellei adhesive properties for rubber compounds containir a high ratio of SBR. The adhesive composition has, 4 course, good adhesion to the NR compounds.

An important point in the process of the present Il vention is to produce the resol type resin by using alkali metal hydroxide as a catalyst by reaction b tween the monohydric phenol and the aldehyde at fir (An acidic material should not be used because a now lac type resin is produced thereby.). A'mmoniumhydroxide or basic organic compounds such asamin'es should not be used as the alkaline catalyst in the present invention. When aminesare used as catalysts,'a complicated reactionoccurs' between the amines and the free aldehyde produced during the reaction; in addition, the amine will react with a phenol to' produce a long chain, water insoluble resin.

lt is also important that free aldehyde should not be present when the separated resinous material is dissolved in ammonium hydroxide. When free aldehyde is present, a long chain, water insoluble resin is produced as mentioned above. This is not desirable.

Representative monohydric phenols which may be used in the present invention are phenol, and alkyl phenols such as cresol, ethyl phenol, xylenol and the like;

the preferred phenols are phenol, m-cresol and pcresol, with phenol being particularly preferred.

It was believed that resorcinol is a most preferred phenol for adhesives since synthetic fibers were used as a reinforcing element. Accordingly, it is not too much to say that the only phenols being used at present are.

resorcinols. n the other hand, it was not known that good results could be obtained through the use of inexpensive and easily available phenol as a component of an adhesive composition. For example, D. M. Sandomirskii et al. reported that adhesive compositions prepared from phenol were inferior to those prepared from resorcinol. (Refer to M. S. Dostyan, D. M. Sandomirskii and P. V. Vaina: Soviet Rubber Technology Vol. 19, No. 9, Page 20-Page 25.).

The effect of formaldehyde resins prepared with resorcinol and phenol has been described in the art. The reaction between phenol and resorcinol with formaldehyde in the preparation of an adhesive solution is depicted by the following reaction sequence:

OH O'Nc oHCHOeNeOH-- Q m O'Nc H. OH

cn on on 4. As indicated by-theabove' re sulting products are and action sequence, the rein thecase of phenol O'NO' in the case of resorcinol.

A composition containing a free hydroxylgroup linked directly to the benzenenucleus exhibits good adhesive properties. The product having no free hydroxyl group linked directly to a benzene nucleus and having an -O'Na* group resulting fromthe hydroxyl group present in the original compounds exhibits only poor adhesive properties. Accordingly, it'has'been believed, prior to the present invention, that an adhesive prepared from resorcinol and formaldehyde is a very good adhesive, which the adhesive prepared from phenol and formaldehyde was believed to be inferior to the product prepared from resorcinol. Phenolformaldehyde resin in the latex was believed to cause no noticeable increase in the bond strength of model systems, the mechanical properties of the films or the bond strength of the system as a whole. Resorcinolformaldehyde resin, on the other hand, was believed to improve the properties of model systems substantially and increase bond strength in the cord-adhesive-rubber system. (c.f. Soviet Rubber Technology Vol. 19, No. 9, pp. 20-25 (1960)).

By the present invention, anexcellent adhesive is provided using, phenol in place of resorcinol. The reaction proceeds according to the following sequence:

O 4 HCHO (H OH "Nc e HCHO e NcON "'z "2 (1 I) o'ua CH OH e CH COO weu out e cu coo'ue in the reaction sequence, reaction (iv) illustrates the reaction which occurs in -the animator a fabric 'material. The reaction products-obtained in'(i), and (iii) are water soluble, and (ii) is water insoluble. (ii) is re,-- moved by filtering. it is desirable that the" components of the adhesivebe soluble inwater since'water isthe mediumgenerally employed for adhesives. lt is ieferred that the resin contains a free OH group linked directly to the benzene nucleus after the heating treatment. This is accomplished by the present invention by mula:

I H OH fr t fi The above mentioned formulas i. ll, (i), (ii), (iii) and (iv) are reaction sequences simplified in order to understand easily the difference of behavior between NaOH and NH,OH and the process of the present invention. in fact the above reactions are more complicated. Furthermore, formaldehyde attacks H radical at para position of phenol.

The present inventors have found that an adhesive composition capable of giving high adhesion strength can be produced by using monohydric phenols such as phenol and the like.

One of the features of the present invention is that the adhesive composition of the present invention gives high adhesion strength between a fabric material and blended compositions of SBR and NR containing a high ratio of SBR, or a composition of SBR alone as well as a composition of NR alone.

The aldehyde used in the present invention is a compound having an aldehyde radical and reactivity with phenols. Aldehydes such as furfural, acrolein and the like may be employed, but formaldehyde is the most preferred aldehyde. Further, there may be used aldehyde polymers such as para formaldehyde, alpha polyoxymethylene, beta polyoxymethylene', polyoxymethylene glycol derivative, trioxane, tetraoxane and the like.

in the present invention, the reaction temperature of the reaction between the phenol and the aldehyde in the presence of the alkali metal hydroxide is preferably from 30C. to.l'C. at ordinary pressure; the preferred temperature range is from 70C. to 95C. The reaction time is determined appropriately depending upon temperature, the amount of catalyst, and the like. For example. where a reaction temperature of 80C. is employed. it is preferable to employ sufficient catalyst so that the reaction time is from about l hour to 3 hours. The amount of alkali metal hydroxideused as catalyst is suitably from 0.01 mole to 0.02 moles per mole of phenol; the preferred amount is from 0.05 moles to 0.15 moles.

6 The ratio of aldehyde to phenol is important; tl amount of aldehyde is suitably from about 4 moles 10 moles. The preferred ratio is from about 4 moles l0 .moles per, 1' mole of phenol.

-5 Theprogressof the reaction can be detennined I thechange of the average'rnolecular weight and the di tribution curve of the molecular weight. The avera; molecular weight of the reaction product is suitab 'from200 to 2,500, and preferably, from 500 to 1,50

After the: reaction is complete,-the resin thus pr duced can be separated by adding dropwise an organ acid such as acetic acid or an inorganic acid such as h drochloric acid or by pouring the reaction product in the acid. a

The material thus separated is filtered, washed, dril in air or dried under reduced pressure to obtain a resi 'o'us material'useful for adhesion. if the material th separated is dissolved in an organic solvent having low boiling point such as acetone at the wet stage t fore drying andthen is evaporatedand dried under I duced pressure, the resinous material is obtained mo rapidly. p

When free aldehyde remains in the resinous materi formaldehyde is generated, and in practical use of t resinous material, it is harmful to the human body; fi thermore, it causes insolubility of the resinous mater in ammonium hydroxide in the later process. The prc lem is prevented by employing the separation step.

The upper limit of the amount of aldehyde in t composition is not set but, from an economical point view, it is preferable that the upper limit of the amot of aldehyde in the composition be about 10 moles i 1 mole of phenol.

The above resinous material can be easily dissolv in dilute aqueous solution of ammonium hydroxit When the molecular weight of the resinous materia large, the amount of ammonium hydroxide may be creased.

The adhesive solution is prepared by mixing rubl latex with the above-mentioned ammoniacal solutil Natural rubber latex or various synthetic rubber lati are contained in the rubber latex employed in the pr ent invention. In particular, vinylpyridine styrene bu diene terpolymer latex, styrene-butadiene copolyr latex, polybutadiene latex and the like may be us Polychloroprene latex, acrylonitrile-acrylic butadh copolymer latex, acrylonitrile-acrylic-butadiene 1 polymer latex, acrylonitrilalkyl m-acrylate butadit terpolymer latex isoprene isobutylene copolymer lat halogenated isoprene isobutylene copolymer latex, e ylene propylene non-conjugated diene terpolymer tex, chlorinated polyethylene latex, chlorosulfona polyethylenelatex, and the like, may be used. The r ber latices may be used alone or mixtures of twc moremay be employed.

The concentration of the solid portion of the ac sive composition is from about i to 50%, but is pref bly from about l5 to The amount of the resin material is from about 2 parts to 50 parts, per lOO p of thesolid of the rubber latex, preferably from at l0 parts to 40 parts, and most preferably, from at 20 parts to 35 parts.

A synthetic fabric material is coated with the at sive solution by dipping or spraying and then dried.

' drying temperature may be from about 100C.

temperature about 5C; lower than the melting poi: the fabric material employed. A temperature as big possible is generally employed since this will shorten the treating time.

The amount of the adhesive compositionattached to a fabric material is from about 1 part to i5 parts per lparts of fabric material. preferably frorn 3 parts to 5 8 parts. The amount'thus attachedcan be controlled'byi Y the concentration of the: adhesive composition;

The advantage of the-adhesive composition of the present invention is that theadhesive composition can be put in practical use just after being produced by dis solving the resinous material in dilute ammonium hydroxide and mixing with rubber latex. Even if the adhesive composition is allowed to stand for more than one month after being produced. the adhesive strength is not decreased. Onthe contrary, a conventional RFL can not be put into practical use unless RFL stands and ages for sixteen hours afterbeingproduced. and can not be used for as long a period as the adhesive composition of the present invention.

The resinous material is easily dissolved in ammonium hydroxide and a transparent solution is obtained. if the resinous material is dissolved in ammonium hydroxide in the presence of free aldehydeflhe resinous material will react with the free aldehyde to produce a white precipitate which is not soluble in water. In the present invention, the resinous material is dissolved in ammonium hydroxide in the absence of free aldehyde. The process of the present invention is remarkably different from the conventional process in the above point.

EXAMPLE I One hundred parts (l.l moles) of phenol. 440 parts (5.4 moles) of 37% formalin and 20 parts (0.12 moles) of 6N caustic soda were reacted with stirring together 4 in a flask fixed with a reflux condenser at 80C. for 1.5 hours. The solution was then cooled and neutralized with 6N acetic acid and a precipate settled out of solution.

The precipitate was collected by a centrifugal separator, dissolved in 500 parts of acetone, evaporated and dried under reduced pressure, and crushed to a power of resinous material. Forty parts of said resinous material was dissolved in dilute ammonium hydroxide (50 parts of 28% ammonium hydroxide was diluted with 550 parts of water) to obtain a uniform, clear solution. The resulting solution was mixed with 400 parts of vinylpyridine styrene butadiene terpolymer latex (.ISR 0650, manufactured by Japan Synthetic Rubber Co.), stirred sufficiently and immediately put in practical use as an adhesive solution.

The 6-Nylon cord of i260 B12 was dipped in the adhcsive solution and was dried at l90C. for 5 minutes. The rubber compositions A and B were prepared as shown in Table l. Composition A is a blended rubber composition of NR and SBR containing a high ratio of NR. and composition 8 is a blended rubber composition containing high ratio of SBR.

treated with the adhesive solution of the present invention Kg/cord The adhesive strength was measured as follows. The treated cords were set near the surface of the unvulcanized rubber composition sheet 1 and were vulcanized under a pressure of 30kg/cm' at,l 50C. for 20 minutes. One cord was separated from said vulcanized rubber sheet at the speed of 30cm/min. to measure separation resistance. The separation resistance per one cord was designated as the adhesive strength.

Comparison Example Conventional RFL was tested and the following resuitswere obtained:

RFL was produced as follows:

Eleven parts (0.1 mole) of resorcinol was dissolved in 519 parts of water; 16.2 parts (0.2 moles) of 37% formalin was added thereto. 10 parts (0.025 mole) of l0% aqueous solution of caustic soda was added immediately, the mixture was allowed to stand for four hours; 244 parts of 40% vinylpyridine styrene butadiene terpolymer latex (.ISR 0650, manufactured by Japan Synthetic Rubber Co.) was added, and thereafter. the mixture was aged for sixteen hours.

The preparation of test pieces and test were carried out by the same process as in Example I. The test results are as shown in Table 2. The rubber compositions A and B were the same as those of Example 1.

Table 2 Rubber composition Adhesive strength 2.6 (kg/cord) From Table l and Table 2, it is found that the adhesive composition of the present invention is not different from RFL for the rubber composition containing a low ratio of SBR, but is remarkably better than RFL for the rubber composition containing high rate of SBR.

EXAMPLE 2 m-cresol was used in place of phenol in Example I. The result was as shown in Table 3.

9 a Table 3 Rubber composition A 8 Adhesive stren I 2.0

gm (kg/cord) mcresol is as good an adhesive as phenol.

What is claimed is:

1. In a process for makings synthetic fabric-torubber adhesive having improved stability and improved adhesion for bondingsynthetic fabric and natural rubber, styrene-butadiene copolymer and high ratio blends of styrene-butadiene-natural rubber copolymers comprising mixing a synethic rubber latex with an aqueous, alkaline, aldehyde-free resole solution; the improvement comprising preparing said resole by reacting one mole of a monohydric phenol selected fro: phenol and an alkyl phenol with from about 4-l0 molt of formaldehyde or an aldehyde polymer, in a solven employing an alkali metal hydroxide catalyst at a ten perature from about 30 l00C. to form a resole res having a molecular weight from about 200 to 250 separating saidresole resin by neutralizing the reactic mixture with an acid drying and; dissolving the sep rated resin in dilute ammoniacal solution free of ald hyde and thereafter mixing the resulting solution wi the rubber latex in the weight ratio of 2 50 parts res per parts rubber latex solids.

2. The process of claim 1 including employing fro about l0 40 parts of resole resin per 100 parts rubb latex solids.

3. The synthetic fabric-to-rubber adhesive produ prepared by the process of claim 1.

i I i l t 

1. IN PROCESS FOR MAKING A SYNTHETIC FABRIC-TO-RUBBER ADHESIVE HAVING IMPROVED STABILITY AND IMPROVED ADHESION FOR BONDING SYNTHETIC FABRIC AND NATURAL RUBBER, STYRENEBUTADIENE COPOLYMER AND HIGH RATIO BLENDS OF STYRENEBUTADIENE-NATURAL RUBBER COPOLYMERS COMPRISING MIXING A SYNETHIC RUBBER LATEX WITH AN AQUEOUS, ALKALINE, ALDEHYDE-FREE RESOLE SOLUTION; THE IMPROVEMENT COMPRISING PREPARING SAID RESOLE BY REACTING ONE MOLE OF A MONOHYDROC PHENOL SELECTED FROM PHENOL AND AN ALKYL PHENOL WITH FROM ABOUT 4-10 MOLES OF FORMALDEHYDE OR AN ALDEHYDE POLYMER, IN A SOLVENT, EMPLOYING AN ALKALI METAL HYDROXIDE CATALYST AT A TEMPERATURE FROM ABOUT 30* - 100*C. TO FORM A RESOLE RESIN HAVING A MOLECULAR WEIGHT FROM ABOUT 200 TO 2500; SEPARATING SAID RESOLE RESIN BY NEUTRALIZING THE REACTION MIXTURE WITH AN ACID DRYING AND; DISSOLVING LTHE SEPARATED RESIN IN DILUTE AMMONIACAL SOLUTION FREE OF ALDEHYDE AND THEREAFTER MIXING THE RESULTING SOLUTION WITH THE RUBBER LATEX IN THE WEIGHT RATIO OF 2 - 50 PARTS RESIN PER 100 PARTS RUBBER LATEX SOLIDS.
 2. The process of claim 1 including employing from about 10 - 40 parts of resole resin per 100 parts rubber latex solids.
 3. The synthetic fabric-to-rubber adhesive product prepared by the process of claim
 1. 